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auxetic mechanical metamaterials: from soft to stiff

International Journal of Extreme Manufacturing 2023年第4期5卷 60-85页

作者： Xiang Li Weitao Peng Wenwang Wu Jian Xiong Yang Lu School of Sciences Nanjing University of Science and TechnologyNanjing 210094People’s Republic of China School of Naval Architecture Ocean and Civil EngineeringShanghai Jiao Tong UniversityShanghai 200240People’s Republic of China Center for Composite Materials and Structures Harbin Institute of TechnologyHarbin 150001People’s Republic of China Nano-Manufacturing Laboratory(NML) CityU-Xidian Joint Laboratory of Micro/NanoManufacturingShenzhen Research Institute City University of Hong KongShenzhen 518057People’s Republic of China Department of Mechanical Engineering City University of Hong KongKowloonHong Kong Special Administrative Region of ChinaPeople’s Republic of China Chengdu Research Institute City University of Hong KongChengdu 610200People’s Republic of China Department of Mechanical Engineering The University of Hong KongPokfulamHong Kong Special Administrative Region of ChinaPeople’s Republic of China

auxetic mechanical metamaterials are artificially architected materials that possess negative Poisson’s ratio,demonstrating transversal contracting deformation under external vertical compression loading.Their physical properties are mainly determined by spatial topological configurations.Traditionally,classical auxetic mechanical metamaterials exhibit relatively lower mechanical stiffness,compared to classic stretching dominated architectures.Nevertheless,in recent years,several novel auxetic mechanical metamaterials with high stiffness have been designed and proposed for energy absorption,load-bearing,and thermal-mechanical coupling applications.In this paper,mechanical design methods for designing auxetic structures with soft and stiff mechanical behavior are summarized and classified.For soft auxetic mechanical metamaterials,classic methods,such as using soft basic material,hierarchical design,tensile braided design,and curved ribs,are proposed.In comparison,for stiff auxetic mechanical metamaterials,design schemes,such as hard base material,hierarchical design,composite design,and adding additional load-bearing ribs,are proposed.Multi-functional applications of soft and stiff auxetic mechanical metamaterials are then reviewed.We hope this study could provide some guidelines for designing programmed auxetics with specified mechanical stiffness and deformation abilities according to demand.

关键词： auxetic mechanical metamaterial soft stiff structural design

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On the application of additive manufacturing methods for auxetic structures: a review

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Advances in Manufacturing 2021年第3期9卷 342-368页

作者： Athul Joseph Vinyas Mahesh Dineshkumar Harursampath Nonlinear Multifunctional Composites Analysis and Design(NMCAD)Laboratory Department of Aerospace EngineeringIndian Institute of ScienceBangalore560012India Department of Mechanical Engineering National Institute of TechnologySilcharAssam788010India

auxetic structures are a special class of structural components that exhibit a negative Poisson’s ratio(NPR)because of their constituent materials,internal microstructure,or structural geometry.To realize such structures,specialized manufacturing processes are required to achieve a dimensional accuracy,reduction of material wastage,and a quicker fabrication.Hence,additive manufacturing(AM)techniques play a pivotal role in this context.AM is a layer-wise manufacturing process and builds the structure as per the designed geometry with appreciable precision and accuracy.Hence,it is extremely beneficial to fabricate auxetic structures using AM,which is otherwise a tedious and expensive task.In this study,a detailed discussion of the various AM techniques used in the fabrication of auxetic structures is presented.The advancements and advantages put forward by the AM domain have offered a plethora of opportunities for the fabrication and development of unconventional structures.Therefore,the authors have attempted to provide a meaningful encapsulation and a detailed discussion of the most recent of such advancements pertaining to auxetic structures.The article opens with a brief history of the growth of auxetic materials and later auxetic structures.Subsequently,discussions centering on the different AM techniques employed for the realization of auxetic structures are conducted.The basic principle,advantages,and disadvantages of these processes are discussed to provide an in-depth understanding of the current level of research.Furthermore,the performance of some of the prominent auxetic structures realized through these methods is discussed to compare their benefits and shortcomings.In addition,the influences of geometric and process parameters on such structures are evaluated through a comprehensive review to assess their feasibility for the later-mentioned applications.Finally,valuable insights into the applications,limitations,and prospects of AM for auxetic structures are provided to enable the readers to gauge the

关键词： auxetic Additive manufacturing(AM) Negative Poisson’s ratio(NPR) Mechanical performance Unit-cell structure

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Plate-based cylinder metamaterial with negative Poisson's ratio and outstanding mechanical performance

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Science China(Technological Sciences) 2023年第3期66卷 793-806页

作者： LI Xiang XIAO Ran CHEN JuZheng LI JingQi FAN Rong SONG Jian LU Yang School of Sciences Nanjing University of Science and TechnologyNanjing 210094China Nano-Manufacturing Laboratory(NML) Shenzhen Research Institute City University of Hong KongShenzhen 518057China Department of Mechanical Engineering City University of Hong KongHong Kong 999077China College of Civil and Transportation Engineering Shenzhen UniversityShenzhen 518060China CityU-Xidian Joint Laboratory of Micro/Nano-Manufacturing Shenzhen 518057China

Plate-based cellular materials exhibit greater stiffness and strength than conventional cellular materials formed by struts.In this study,we designed and fabricated a plate-based auxetic cylinder metamaterial using high-resolution projection micro-stereolithography three-dimensional printing technique.Experiment and modeling results validated the auxetic behavior of the plate-based cylinder.The normalized Young’s modulus and yield strength of a four-layer auxetic cylinder are increased by 141%and 32%,respectively,compared with the conventional auxetic honeycomb.This study presents a universal strategy for fabricating plate-based auxetic metamaterials with appropriate mechanical performance for various structural applications.

关键词： auxetic plate-based cylinder mechanical metamaterial 3D printing

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auxetic Woven Fabrics—Pores' Parameters Observation

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Journal of Donghua University(English Edition) 2013年第5期30卷 416-420页

作者： VYSANSKA Monika VINTROVA Petra Department of Textile Technologies Faculty of Textile EngineeringTechnical University of Liberec Department of Design Faculty of Textile EngineeringTechnical University of Liberec

Manufacturing of a macro-scale helix auxetic yarn(HAY)was described. Consequently areal woven fabric and three kinds of woven fabrics various in weaves were introduced respectively. Their expected auxetic effect( assured by double helix yarn) was tested through the Poisson's ratio value(for auxetic structure is negative).Other observed parameters talked about variation in woven fabric porosity and the pores' parameters during the sample straining.Setting of this non-standard test( connection between dynamometer and image analysis) was also introduced. The differences among observed parameters were evaluated and conclusions for three types of woven fabrics were determined. It was found that less auxetic behavior caused less porosity. Less auxetic structure( satin) with longer floating threads embodies bigger pores' size and less circularity. The plain pattern has the greatest porosity but the smallest pores; the satin pattern behaves by contraries.

关键词： auxetic behavior helical auxetic yarn(HAY) pores woven fabric

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MOLECULAR DESIGN OF NEW KINDS OF auxetic POLYMERS AND NETWORKS

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Chinese Journal of Polymer Science 2004年第4期22卷 355-362页

作者：魏高原 Department of Polymer Science and Engineering College of Chemistry & Molecular Engineering Peking University Beijing 100871 China

Three new kinds of molecular networks are designed and predicted to exhibit negative Poisson ratios. Molecular mechanics calculations on these networks show that the magnitude of Poisson ratios depends on the relative flexibility of beam and arm structures. Several new kinds of auxetic polymers, whose successful synthesis should be easier than that of the corresponding auxetic networks, are then proposed. It is found that the kabob-like polymers with auxegens lying vertically on the main chain can acquire auxeticity while those with auxegens lying horizontally on the main chain cannot. Besides, a half kabob-like or pseudo-ladder polymer with auxegens linked at the intersection of the beam and the arm does show auxeticity when adopting constrictive conformers. It is, however, worthwhile noting that the origins of auxeticity still await and strongly deserve further experimental and theoretical investigations.

关键词： auxetic auxeticity Negative Poisson ratio auxetic polymer Molecular modeling

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Enhancing buckling capacity of a rectangular plate under uniaxial compression by utilizing an auxetic material

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Chinese Journal of Aeronautics 2016年第4期29卷 945-951页

作者： Zhang Yongcun Li Xiaobin Liu Shutian State Key Laboratory of Structural Analysis for Industrial Equipment Department of Engineering Mechanics Dalian University of Technology

auxetic materials have previously been shown to enhance various performances due to its unusual property of becoming fatter when uniaxially stretched and thinner when uniaxially compressed(i.e., the materials exhibit a negative Poisson's ratio). The current study focuses on assessing the potential of an auxetic material to enhance the buckling capacity of a rectangular plate under uniaxial compression. The in-plane translational restraint along the unloaded edges that was often neglected in open literature is taken into consideration in our buckling model proposed in this study. The closed-form expressions for the critical buckling coefficient of the rectangle are provided and the predicted results agree well with those determined by the finite element method. Furthermore, the results indicate that the buckling performance of a rectangular plate under uniaxial compression can be significantly improved by replacing the traditional material that has a positive Poisson's ratio with an auxetic material when there is in-plane translation restraint along the unloaded edges.

关键词： auxetic material Buckling Elastically restraint Negative Poisson’s ratio Optimization

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Geometric Study of Two-Dimension Stellated Reentrant auxetic Structures to Transformable Architecture

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Journal of Architectural Environment & Structural Engineering Research 2023年第1期6卷 17-24页

作者： MªDoloresÁlvarez Elipe Facultad de Artes y Humanidades URJCMadrid28032Spain

Transformable architecture is totally linked to the study and knowledge of geometry.There are some materials in nature,whose geometric invariants establish equivalent structural behavior regarding the scalar transformations,developing different spatial typologies according to dimensional variation.auxetic materials are characterized by their negative Poisson’s ratio.They can change their geometric configuration from a line to a surface,and from a surface to a volume or spatial framework.This paper is based on establishing and comparing those stellated reentrant auxetic geometries to be able to build new spaces defined by their capacity for architectural transformation,studying analytically geometric properties of stellated reentrant auxetic structures that,from the molecular to the macroscopic level,can be part of the architecture construction.In this investigation,a comparative study by means of CAD of stellated reentrant auxetic patterns has been realized.A Computer-Aided Design study of stellated reentrant auxetic structures will be realized to use them in architecture.The geometric behavior of the different stellated reentrant auxetic patterns is analyzed from the developed study to generate a systematic comparison,evaluating properties of these forms,such as their maximum achievable area reductions in relation to the total length of bars of the structure,in order to obtain a growth factor.

关键词： Transformable Architecture Geometry auxetic Stellated Reentrant CAD Growth factor

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Structural metamaterials with negative mechanical/thermomechanical indices: A review

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Progress in Natural Science:Materials International 2021年第6期31卷 801-808页

作者： Jo?o O.Cardoso Jo?o Paulo Borges Alexandre Velhinho CENIMAT/i3N Departamento de Ciência dos Materiais Faculdade de Ciências e Tecnologia Universidade Nova de Lisboa

Structural metamaterials presenting negative values of one or more mechanical and thermomechanical indices–namely the Poisson's ratio, the linear compressibility, and the coefficient of thermal expansion – are the promising candidates to the applications in many fields, ranging from precision mechanics to biomedical devices or energy absorption. Although scattered mentions may be found in the literature since the late eighties of 20th century, the systematic research efforts concerning these materials became effective much later. The present work is to review the main scientific contributions to the topic in the last five years. This paper first deals with those metamaterials showing a single negative index, and then proceeds to analyze the much less frequent instances of coupled negative indices, with emphasis on the so-called anepectic case, which exhibits an unusual thermomechanical response.

关键词： Mechanical and thermomechanical metamaterials auxetic Anepectic Negative Poisson's ratio Negative thermal expansion Negative linear compressibility

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Using of an auxetic Structure as Reinforcement of a Bending Reinforced Concrete Beam

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Journal of Mechanics Engineering and Automation 2019年第1期9卷 1-16页

作者： Tarik Baran Department of Civil Engineering Osmaniye Korkut Ata UniversityOsmaniye 80000Turkey

Materials which have negative Poisson’s ratio are entitled as auxetics.auxetics can be designed as micro-to macro-sized structures.The use of auxetics in civil engineering structures has been studied only to a limited extent.In this study,a re-entrant medium-size auxetic structure is employed as reinforcement of a reinforced concrete beam.The beam is subjected to static and dynamic loading conditions and then investigated by means of maximum vertical displacements of the beam.Besides,normal stresses and shear stresses of the concrete are also assessed.To interpret the performance of the auxetic reinforcement,obtained results are compared with the results of another beam which has non-auxetic reinforcement.The results show that these structures behave with bending compatibility as expected and due to the negative Poisson’s ratio,they led to shear strength increase.auxetic structures can be employed as reinforcement in a beam.Besides,they can be employed without concrete to increase the shear strength in the case of high shear and impact strength if it is needed.

关键词： auxetic re-entrant cell structure negative Poisson’s ratio auxetic reinforcement indentation resistance

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Modified virtual internal bond model based on deformable Voronoi particles

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力学快报：英文版 2020年第2期10卷 87-91页

作者： Oleg Konovalov Shunying Ji Michael Zhuravkov Research Laboratory of Information Technologies and Computer Graphics Belarusian State UniversityMinsk 220030Belarus DUT-BSU Joint Institute Dalian University of TechnologyDalian 116023China State Key Laboratory of Structural Analysis for Industrial Equipment Dalian University of TechnologyDalian 116023China Department of Theoretical and Applied Mechanics Belarusian State UniversityMinsk 220030Belarus

In last time,the series of virtual internal bond model was proposed for solving rock mechanics problems.In these models,the rock continuum is considered as a structure of discrete particles connected by normal and shear springs(bonds).It is well announced that the normal springs structure corresponds to a linear elastic solid with a fixed Poisson ratio,namely,0.25 for threedimensional cases.So the shear springs used to represent the diversity of the Poisson ratio.However,the shearing force calculation is not rotationally invariant and it produce difficulties in application of these models for rock mechanics problems with sufficient displacements.In this letter,we proposed the approach to support the diversity of the Poisson ratio that based on usage of deformable Voronoi cells as set of particles.The edges of dual Delaunay tetrahedralization are considered as structure of normal springs(bonds).The movements of particle’s centers lead to deformation of tetrahedrals and as result to deformation of Voronoi cells.For each bond,there are the corresponded dual face of some Voronoi cell.We can consider the normal bond as some beam and in this case,the appropriate face of Voronoi cell will be a cross section of this beam.If during deformation the Voronoi face was expand,then,according Poisson effect,the length of bond should be decrees.The above mechanism was numerically investigated and we shown that it is acceptable for simulation of elastic behavior in 0.1–0.3 interval of Poisson ratio.Unexpected surprise is that proposed approach give possibility to simulate auxetic materials with negative Poisson’s ratio in interval from–0.5 to–0.1.

关键词： Discrete element method Real multi-dimensional internal bond Voronoi tessellation Micromechanical poisson ratio Barycentric coordinates auxetic effects

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